1. Field of the Invention
This invention relates to a tape recorder of the type wherein stopping of a reel receiving member is detected to activate a particular mechanism of the tape recorder such as an automatic stopping mechanism or an automatic reversing mechanism.
2. Description of the Prior Art
Tape recorders are already known wherein when a reel receiving member is stopped, for example, at an end of a tape, an automatic stopping mechanism, an automatic reversing mechanism or some other mechanism is activated.
In a conventional tape recorder of the type described, a tape tension detecting member is mounted on a head carrying member on which a magnetic head is carried, and in a reproduction or recording operating mode of the tape recorder, the tape tension detecting member is pressed against a magnetic tape at a position near the magnetic head so that the tape travels along a partially bent or curved path.
Accordingly, when the tape comes to its end in the reproduction or recording operating mode of the tape recorder, the tension of the tape will increase suddenly and thus attempt to straighten the partially bent or curved portion of the tape. This will push the detecting member to move back to its home position. Such movement of the detecting member then is thus used to activate a particular mechanism of the tape recorder such as an automatic stopping mechanism or an automatic reversing mechanism.
Since in a reproduction or recording operating mode of the tape recorder the tape tension detecting member is pressed against a magnetic tape so that the tape runs along a partially bent or curved path in this manner, the conventional tape recorders have following problems:
(1) Since a magnetic tape is pressed by the detecting member, the resistance to the tape during running is high. Consequently, the contacting pressure of a pinch roller to a capstan must be high accordingly, and hence a spring is necessitated which provides such a high contacting pressure. As a result, the capstan undergoes a high lateral pressure, which make designing of a bearing difficult. Besides, a high operating force is required for reproduction or recording operation.
(2) Since a tape runs along a partially bent or curved path, running of the tape is unstable, which is particularly remarkable at a joint of tapes.
Also a rotation stopping detecting mechanism for a tape recorder is already known which directly detects stopping of rotation of a reel receiving member at an end of a tape.
Referring to FIG. 17, there is shown a tape recorder in which such a rotation stopping detecting mechanism in incorporated. The tape recorder shown includes a main base plate 101, a reel shaft 102 securely mounted on and extending upwardly from the main base plate 101, and a unitary structure of a reel receiving member 103 and a sleeve 105 mounted for rotation round the reel shaft 102. The sleeve 105 has a flange 104 formed at a lower end thereof.
A gear 107 is mounted for rotation on an upper face of the flange 104 of the sleeve 105 with a felt plate 109 interposed therebetween, and a compression coil spring 108 is interposed between the gear 107 and the reel receiving member 103. An engaging projection 112 is formed on the extends downwardly from a lower face of the gear 107. A detecting member 110 in the form of a flat plate is mounted for rotation on a lower face of the flange 104 of the sleeve 105 with another felt plate 109 interposed between, and another compression coil spring 111 is interposed between the detecting member 110 and the main base plate 101.
If a turning force of a motor not shown is applied to the gear 107, it is transmitted to the reel receiving member 103 via the felt plate 106 on the upper face side of the flange 104 and further to the detecting member 110 via the felt plate 109 on the lower face side of the flange 104. An operating member 113 is normally located at a portion thereof in a locus of turning motion of the detecting member 110 so that, during rotation of the gear 107, the operating member 113 may be engaged by the detecting member 110 and thus normally acted upon by an uging force or turning torque of the detecting member 110. If the reel receiving member 103 is stopped from rotation due to an excessive load applied thereto, then the urging force will no more act upon the detecting member 110. Consequently, the operating member 113 is displaced by a biasing force of a spring not shown to a predetermined position in which part of the operating member 113 is positioned on a locus of turning motion of the engaging projection 112 on the lower face of the gear 107.
With the construction of the rotation stopping detecting mechanism, when the reel receiving member 103 is stopped, part of the operating member 113 is moved into the locus of turning motion of the engaging projection 112 on the gear 107. Consequently, the operating member 113 is subsequently moved compulsorily against the biasing force of the spring not shown by the turning force of the gear 107. Accordingly, if an automatic stopping mechanism or an automative reversing mechanism is associated with the operating member 113 such that the former may be rendered operative by such compulsory movement of the latter, then the former will be operated by the turning force of the drive motor not shown in response to stopping of the reel receiving member 103.
With the conventional rotation stopping detecting mechanism having such a construction as shown in FIG. 17, however, in order to exert a turning torque or urging force in the same direction as the direction of rotation of the reel receiving member 103 to the detecting member 110, the felt plate 109 is interposed between the the flange 104 integral with the reel receiving member 103 and the detecting member 110, and the detecting member 110 is biased toward the flange 104 by the compression coil spring 111. It is therefore difficult to reduce the dimension of the rotation stopping detecting mechanism in the axial direction. Accordingly the conventional rotation stopping detecting mechanism is disadvantageous to an application wherein it is required to have a relatively small axial dimension. Besides, it is desired to minimize the number of components eliminating such a compression coil spring or a felt plate as described above in order to reduce the production cost.